Abstract:Ecological impact of Eucalyptus plantation is a key scientific topic of global concern, especially its deforestation and water safety problem. Present research findings have evolved around the black water mechanism, its characteristics and the source of the dark component. The driving factor of black water, its prediction and adaptive control have been analyzed in this study. Research has indicated that black water appeared in depressions, streams and reservoirs of different scale in the eucalyptus forest. This was mainly caused by dissolved organic carbon and tannic acid that was extracted from eucalyptus leaf. Black complex formed by the combination of tannic acid with metal ions, and ferrous metal sulfides formed when the water was oxygen deficient. Besides, black water formation was triggered by either a change in meteorological conditions, hydrological situation or sediment accumulation, and migration. For deep waters(large and medium-sized reservoirs), which are affected by thermal stratification, dark matter accumulated in the water bottom. The water’s thermal stratification structure lost its stability when the temperature dropped, hence allowed the mixing of the water along the column in the reservoir leading to various chemical reactions, then finally caused the appearing of black water. Additionally, when the hydrological regime suddenly changes, the flood water that flows into the reservoir in the form of underflow will bring large amounts of DOC, plant residue and sediment into the water, resulting in the black water. The decomposition of microorganisms and the release of nitrogen as well as phosphorus in sediments aggravated oxygen deficiency at the bottom of the water, and created an environment for the formation of black matter. To predict and control the black water, it is very important to establish a model to simulate the transportation and regulate the adaptability of it. Present research was focused on the small-scale water(such as streams, rivers, etc. ), so the formation mechanism of large-scale water that results in stratification(such as deep lakes and reservoirs, etc. )is still not entirely clear. Therefore, further study on the simulation and prediction of black water at the basin level is needed. At last, the mechanism of reservoirs in eucalyptus forest area will be an important topic in the future.

Abstract:Based on the combination of online monitoring and hydraulic fluid simulation, the distribution of flowing field inside the existing UF membrane component was investigated by means of numerical simulation, tracer technology and high-speed image acquisition and analysis, and new UF membrane components was designed. The results show that the internal flow field of UF membrane component is mainly affected by the cloth pipe, and the uniformity of opening of the water pipe directly affects the uniformity of water distribution inside the UF membrane component. Compared with the component of UFA-860C, the strip-hole UF membrane component has the ability to make better use of the effective area of UF membrane wire at the operating time, thus effectively reducing the membrane pollution.

Abstract:Local precipitation is a precious water resource on the Alxa Desert Plateau of West Inner-Mongolia, Northwest China. The Hydrogen and oxygen isotope compositions in the precipitation of this region were investigated during 2013 and 2015 to explore the influences on precipitation isotopes and to reveal the moisture source of precipitation. The results show that: (a)δD and δ¹⁸O values in the precipitation show a distinct seasonal variation, with higher values in summer and lower values in winter, on the Alxa Desert Plateau. (b)Among main meteorological parameters(precipitation amount, air temperature, atmospheric humidity and wind speed), air temperature is the most predominant factor controlling isotopic compositions of precipitation on both daily and monthly scales. The local meteoric water line is defined by the relationship between δD and δ¹⁸O on the Alxa Desert Plateau and has lower slope and intercept than those of surrounding areas, implying stronger non-equilibrium evaporation of raindrops in this region. (c)In combination with the HYSPLT air mass trajectory model, the evidence of precipitation isotopes suggests there was a dominant control of westerly and polar air masses on the Alxa Desert Plateau, and the moisture of local precipitation mainly originated from the north and west throughout all the year.

Abstract:To study the adverse effect of wavebreak forest on river flood, a numerical model was constructed using MIKE21 FM model, and the wavebreak forest was described by the structure to build the numerical model. Outputs including water level before the dike, average cross-section water level and cross-section velocity were quantitatively compared between conditions with and without wavebreak forest to analyze the effect. The Dongyang Dike of Nenjiang River was taken as an example, and results show that the wavebreak forest influences the changes of water level and velocity. The wider the forest, the greater the water depth, and the greater the influence of wavebreak forest on the flood discharge. Meanwhile, the effect of wavebreak forest on flood discharge capacity is very small under current condition and designed condition on the Dongyang reach.

Abstract:Based on set-pair analysis theory and triangular fuzzy number theory, the state evaluation model of water resources carrying capacity was established. Through theoretical analysis, frequency calculation and data statistics, 14 indexes were selected, and each index was divided into five grades, to establish an evaluation index system of water resources carrying capacity. The weight of each index was calculated by means of combination of subjective and objective weights, and the main influencing factors and reasons of water resources carrying capacity were analyzed. Based on the connection number method, the situation of water resources carrying capacity of each sample was analyzed by set-pair subtractive situation. With the data of 17 cities in Shandong Province in 2015, the results were analyzed. The results show that: main factors that affect the water resources carrying capacity of all cities in Shandong are irrigation water per unit area, groundwater resources per unit area and wastewater discharge per unit area. From four characteristic layers, the weight of natural characteristics of water resources is the largest. The overall carrying capacity of water resources in Shandong is in the state of critical overloading and slight overloading. Under the condition of stable water resources, improving water resources utilization efficiency and improving water environment can effectively improve the carrying capacity of water resources. Through the analysis of examples, the model is practical and effective, and has certain practical significance and value.

Abstract:An interactive numerical calculation method to simulate the real-time substructure shaking table testing for the equipment-high rise structure-soil system was proposed. Considering that the soil is not completely nonlinear under strong earthquakes, locally nonlinear soil model was adopted as the numerical substructure in order to consider the influence of nonlinear soil during the substructure testing. Meanwhile, the equipment-high rise structure system was adopted as the experimental substructure. Then, equations of motion for the equipment-high rise structure-locally nonlinear soil system was derived using the branch modal substructure method and the linear-nonlinear hybrid constraint modal substructure method. A thirteen-layer steel framework system model was used as an analytical example, that the equipment-high rise structure system and locally nonlinear soil computing model were built by MATLAB and ANSYS respectively. Data communication occurred between two parts. Through the numerical result, it is found that the soil-structure interaction(SSI)and the frequency change of equipment have important influences on the seismic response of equipment and structure.

Abstract:In this study, a 2D fluid-solid-coupled numerical model was established based on the investigation data of a station of Tianjin metro line 3, and a series of numerical simulations were carried out to investigate the distribution of horizontal foundation modulus along the depth under conditions of different foundation pit width and dewatering depth. The numerical results are compared with those computed by the m method, which is a traditional design method of foundation pit recommended in the Chinese Code. The results indicate that under the common conditions of pre-excavation dewatering(PED), the horizontal foundation modulus decreases greatly compared with the values determined by the m method, and the larger the pit width and dewatering depth, the greater the decrease extent. When using the elastic foundation beam method to predict the PED-induced deformation of a retaining structure, the obtained deformation will be underestimated, if the m method is used to determine the horizontal foundation modulus.

Abstract:The mechanical behaviors of interface between clay and concrete were investigated by unidirectional direct shear tests under different interfacial water pressure and normal stress conditions, from which the shear strength and stress-strain relations of interface were analyzed. After that, a constitutive model for the interface between clay and concrete was proposed based on the hyperbolic model considering the influence of interfacial water pressure. According to the test, it can be found that there is a hyperbolic relationship between shear stress and shear displacement, and the vertical displacement mainly expresses the shear shrinkage. The shear strength of interface is significantly correlated with the saturation state of soil near the interface. The shear strength of interface decreases obviously with the increase of interfacial water pressure when the surrounding soil changes from unsaturated state into saturated state. However, when the surrounding soil is saturated, the reduction of shear strength with the increase of interfacial water pressure becomes smaller, and the relationship between the shear strength and the effective normal stress is linear. The predicted result by the model corresponds with the experimental data, which illustrates that the proposed model is reasonable and practical.

Abstract:In order to study the influence of bridge deck structure and bridge deck pavement on the mechanical properties of orthotropic steel bridge deck, a reasonable structure was established. The longitudinal stiffeners of the trapezoid and rectangular cross sections were combined with a variety of notch forms to form the orthotropic steel bridge panel structure system, and then, asphalt concrete pavements of different thickness and elastic modulus were laid on the bridge. The finite element solid model of asphalt concrete pavement was established to apply loading. The influence of the cross-section shape of longitudinal stiffener, the gap form, the elastic modulus and thickness of the pavement layer on the mechanical properties of orthotropic steel bridge deck was calculated and analyzed by the finite element method. The results show that if the gap between the stiffeners is small, the force performance of bridge deck can be obviously improved. The stiffener B has better stress performance with less material. The notch I and notch III should be selected rationally, and the notch III needs to be optimized. The stress of the connection between the top plate and the longitudinal rib is high, and the mechanical property is sensitive. Moreover, the elastic modulus and thickness of the paving layer should be designed in a comprehensive way, in order to make the steel bridge deck have the best mechanical performance.

Abstract:In order to reveal the spatiotemporal evolution regularities of the internal microcracks initiation, development and coalescence in rock under cycling loading, using sandstone as the research object, the acoustic emission tests of sandstone in uniaxial cyclic loading and unloading were carried out. The results show that: the propagation velocity of sound wave in rock can be obtained by the wave velocity test in different directions, which can provide reasonable velocity parameters for acoustic emission location; the space position of fracture plane can be accurately located by reasonably arranging the position of the sensor; the number of acoustic emission events and energy present a stepwise increase during the loading and unloading process, indicating that acoustic emission has memory effect; through the comparison between the space location of acoustic emission events and position of rupture surface in the rock sample, two positions are basically the same and the acoustic emission can effectively obtain the whole process of rock crack propagation. The results can provide important technical support for the rock mass stability analysis, which has an important value of engineering application.

Abstract:To study interfacial behavior of concrete structures strengthened with fiber reinforced polymer(FRP)subjected to the freeze-thaw cycling, this study presents experimental investigations on the degradation behavior of FRP laminate-to-concrete interfacial bond performance under combined effects of freeze-thaw cycling and sustained loading with double-lap shear tests. After being exposed up to 200 freeze-thaw cycles, the specimens were tested to failure monotonously. Digital image correlation method was employed to capture the full-field displacement of the specimen during loading. Interfacial bond stress-slip relationship was determined based on the analysis of full-field data. Test parameters included the freeze-thaw cycles, sustained loading and concrete types. Test results show that the freeze-thaw cycling leads to significant decreases in all interfacial parameters. The bond stress-slip relationship is also degenerated with freeze-thaw cycles seriously. When considering the sustained loading, additional interfacial degradations were observed after freeze-thaw cycling. Apparent changes of interfacial failure modes were also observed during tests.

Abstract:At present, the theoretical formulas for determining the width of waterway regulation lines were mostly solved by establishing a certain relationship between the flow and sediment conditions before and after the project. Many parameters were involved in these formulas, and in the solving process, it was usually assumed that value of part parameters in the formula is the same before and after the project. However, some changes may occur before and after the project, affecting the accuracy of the width of regulation lines. In order to avoid errors caused by this assumption, a new method to determine the width of waterway regulation lines was proposed. Based on the mechanism of flow movement, sediment movement and river bed topography, two determining methods for the width of waterway regulation lines under continuous scouring condition and sediment transport equilibrium condition were put forward by theoretical study, and the proposed methods were verified by practical projects with good regulation effect. The results show that the proposed methods have good engineering results, and compared with most existing methods, the width of the regulation lines determined by the new method is the closest one to the actual value of engineering project, which can provide a good theoretical support for waterway regulation projects.

Abstract:A new type of tetrahedron permeable frame was proposed based on the concept of fish shelter, and experiments on the flow characteristics around the protected area were conducted using acoustic doppler current profilers(ADCP). Then, the influences of overhead rates on the flow structure and hydrodynamic characteristics were discussed. The experimental results show that the difference of velocity distributions between the top and bottom of flow is more obvious. The flow velocity of the frame layer is obviously reduced, and the decrease rate of the flow velocity increases with the decrease of the overhead rate. An inflection point appears in the turbulence intensity distribution, and its position has a distinct correlation with the overhead rate. In addition, the turbulence intensity increases with the decrease of overhead rate too. There is a turbulent convergence zone near the bottom of the protective zone, and the turbulence intensity of this zone decreases with the decrease of the overhead rate.